Disk drive with a spherical balance plug

ABSTRACT

Described herein is a balance plug for a disk drive. The balance plug includes a body defining a substantially spherical outer surface and a plurality of ribs along the spherical outer surface and defining at least three meridians along the outer surface of the sphere. The at least three meridians can reside in at least two transverse planes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/826,671, filed on Jun. 30, 2010, which is hereby incorporated byreference in its entirety.

BACKGROUND

Hard disk drives, (HDD) are often used in electronic devices, such ascomputers, to record data onto or to reproduce data from a recordingmedia, which can be a disk having one or more recording surfaces. TheHDD also includes a head for reading the data on a recording surface ofthe disk and for writing data unto one of the surfaces. An actuator isprovided for moving the head over a desired location, or track of thedisk.

The HDD includes a spindle motor for rotating the disk during operation.When the disk drive is operated, and the actuator moves the head overthe disk, the head is floated a predetermined height above the recordingsurface of the disk while the disk is rotated, and the head detectsand/or modifies the recording surface of the disk to retrieve, record,and/or reproduce data from and/or onto the disk.

When the HDD is not in operation, or when the disk is not rotating, thehead can be rotated by the actuator to a position such that the head isnot over the disk or the recording surfaces. In this non-operationalconfiguration, the head is “parked off” of the recording surface of thedisk.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of thedisclosure will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the disclosure and not to limit the scope of thedisclosure. Throughout the drawings, reference numbers are reused toindicate correspondence between referenced elements.

FIG. 1 depicts a perspective view of a disk drive in accordance with oneembodiment.

FIG. 2 illustrates a top view of a disk drive in accordance with oneembodiment.

FIG. 3 illustrates a perspective view of a disk pack in accordance withone embodiment.

FIG. 4A illustrates a perspective view of a portion of a motor hub inaccordance with one embodiment.

FIG. 4B illustrates a perspective view of a portion of a motor hub inaccordance with one embodiment.

FIG. 4C illustrates a perspective view of a portion of a motor hub inaccordance with one embodiment.

FIG. 5 illustrates a partial cross-sectional view of a disk pack inaccordance with one embodiment.

FIG. 6A illustrates one embodiment of a balance plug.

FIG. 6B illustrates one embodiment of a balance plug.

FIG. 6C illustrates one embodiment of a balance plug.

DETAILED DESCRIPTION

Referring now to FIG. 1, there is depicted an exploded perspective viewof a disk drive 10 according to embodiments described herein. The diskdrive 10 includes a head disk assembly (HDA) and a printed circuit boardassembly (PCBA). The head disk assembly includes a disk drive housinghaving disk drive housing members, such as a disk drive base 12 and acover 14. The disk drive base 12 and the cover 14 collectively house atleast one disk 16. A single disk or additional disks may be included inthe disk drive.

The disk 16 includes an inner diameter (ID) 18 and an outer diameter(OD) 20. The disk 16 further includes a plurality of tracks on itsrecording surface, or face, for storing data. The disk 16 may be of amagnetic recording type of storage device, however, other arrangements(e.g., optical recording) may be utilized. The head disk assemblyfurther includes a spindle motor 22 for rotating the disk 16 about adisk rotation axis 24. The head disk assembly further includes a headstack assembly 26 rotatably attached to the disk drive base 12 inoperable communication with the disk 16. The head stack assembly 26includes an actuator 28.

The actuator 28 includes an actuator body and at least one actuator arm32 that extends from the actuator body. Some embodiments includemultiple arms 32. Distally attached to the actuator arms 32 aresuspension assemblies 34. The suspension assemblies 34 respectivelysupport heads 36. The suspension assemblies 34 with the heads 36 arereferred to as head gimbal assemblies. The number of actuator arms andsuspension assemblies may vary depending upon the number of disks anddisk surfaces utilized.

The head 36 can include a transducer for writing and reading data. Thetransducer can include a writer and a read element. In magneticrecording applications, the transducer's writer may be of a longitudinalor perpendicular design, and the read element of the transducer may beinductive or magnetoresistive.

In optical and magneto-optical recording applications, the head may alsoinclude an objective lens and an active or passive mechanism forcontrolling the separation of the objective lens from a disk surface ofthe disk 16. The disk 16 includes opposing disk surfaces. In magneticrecording applications the disk surface typically includes one or moremagnetic layers. Data may be recorded along data annular regions on asingle disk surface or both.

The head stack assembly 26 may be pivoted such that each head 36 isdisposed adjacent to the various data annular regions from adjacent tothe outer diameter 20 to the inner diameter 18 of the disk 16. In FIG.1, the actuator body includes a bore, and the actuator 28 furtherincludes a pivot bearing cartridge 38 engaged within the bore forfacilitating the actuator body to rotate between limited positions aboutan axis of rotation 40.

The actuator 28 can further include a coil support element 42 thatextends from one side of the actuator body opposite the actuator arms32. The coil support element 42 is configured to support a coil 44. AVCM magnet 46 may be supported by the disk drive base 12. Posts may beprovided to position the VCM magnet 46 in a desired alignment againstthe disk drive base 12. A VCM top plate 48 may be attached to anunderside of the cover 14. The coil 44 is positioned, in someembodiments, between the VCM magnet 46 and the VCM top plate 48 to forma voice coil motor for controllably rotating the actuator 28.

The head stack assembly 26 can further include a flex cable assembly 50and a cable connector 52. The cable connector 52 can be attached to thedisk drive base 12 and is disposed in electrical communication with theprinted circuit board assembly. The flex cable assembly 50 suppliescurrent to the coil 44 and carries signals between the heads 36 and theprinted circuit board assembly.

With this configuration, current passing through the coil 44 results ina torque being applied to the actuator 28. The actuator 28 includes anactuator longitudinal axis 64 which extends generally along the actuatorarms 32. A change in direction of the current through the coil 44results in a change in direction of the torque applied to the actuator28, and consequently, the longitudinal axis 64 of the actuator arms 32is rotated about the axis of rotation 40. It is contemplated that othermagnet, VCM plate, coil and magnet support configurations may beutilized, such as a multiple coil arrangements, single or double VCMplates and a vertical coil arrangement.

The disk drive 10 can also include a latch 54. The latch 54 can includea fixed portion 56 that is firmly coupled to the disk drive base 12. Thelatch 54 further includes a latching portion that is engagable withfixed portion 56 to limit rotational movement of the actuator 28.Although the latch 54 is depicted as being located in a corner of thebase, the latch 54 could be located in other portions of the disk driveand still perform its functions.

When the actuator 28 is rotated into the parked position, as illustratedin FIG. 1, the actuator 28 can include a contact member 76, which can belocated on the coil support element 42 or elsewhere, that is configuredto engage a crash stop 80 in order to limit rotation of the actuator 28away from the disk 16. The crash stop 80 can be an integral part of thebase 12, or the crash stop 80 can be connected to the base 12 via afixation element 72. FIG. 1 depicts an axis of engagement 66 of thecontact member 76 and the crash stop 80 as being in line with thefixation element 72, but other constructions are also permissible. Acrash stop 80 can also be provided to limit movement of the actuator 28toward the ID 18 of the disk 16.

Data is recorded onto a surface of the disk in a pattern of concentricrings known as data tracks. The disk surface is spun at high speed bymeans of a motor-hub assembly. Data tracks are recorded onto the disksurface by means of the head 36, which typically resides at the end ofthe actuator arm 32. One skilled in the art understands that what isdescribed for one head-disk combination applies to multiple head-diskcombinations.

The dynamic performance of the HDD is a major mechanical factor forachieving higher data capacity as well as for manipulating the datafaster. The quantity of data tracks recorded on the disk surface isdetermined partly by how well the head 36 and a desired data track canbe positioned relative to each other and made to follow each other in astable and controlled manner. There are many factors that can influencethe ability of the HDD to perform the function of positioning the head36 and following the data track with the head 36. In general, thesefactors can be put into two categories; those factors that influence themotion of the head 36; and those factors that influence the motion ofthe data track. Undesirable motions can come about through unwantedvibration and undesirable tolerances of components.

During development of the HDD, the disk 16 and head 36 have undergonereductions in size. Much of the refinement and reduction has beenmotivated by consumer request and demand for more compact and portablehard drives 10. For example, the original hard disk drive had a diskdiameter many times larger than those being developed and contemplated.

Smaller drives often have small components with relatively very narrowtolerances. For example, disk drive heads 36 are designed to bepositioned in very close proximity to the disk surface. Due to the tighttolerances, vibration activity of the actuator arm 32 relative to thedisk 16 can adversely affect the performance of the HDD. For example,vibration of the actuator 28 can result in variations in the spacingbetween the head element and media. Additionally, irregular movement ofthe disk 16, or vibrations caused by unbalanced rotations, can result invariations in the spacing between the head element and the disk 16, ormedia.

In addition, as disk drive tracks per inch (TPI) increases, sensitivityto small vibrations also increases. Small vibrations can causesignificant off-track and degraded performances. For example, in manycases, variations in the spacing between the head element and media canincrease the off-track complications, and the increase in TPI compoundsthe complications and likely gives rise to data errors. These dataerrors can include both hard errors during writing and soft errorsduring reading. Moreover, vibration-induced errors become even moreapparent as the actual offset distances and overall components arereduced in size.

Each disk 16 is mounted on a rotatable hub 98 connected to the spindlemotor 22 and is secured to the rotatable hub by a disk clamp 100, asillustrated in FIG. 2. Some disk drives 10 include a plurality of disks16 to provide additional disk surface for storing greater amounts ofdata. The resulting combination is referred to herein as a motor/diskassembly or as a disk pack 102.

Multiple data storage disks 16 can be mounted on the rotatable hub 98 invertically and substantially equally spaced relations. One or morebearings 104 are disposed between a motor or spindle shaft 106 and therotatable hub 98, which is disposed about and rotatable relative to thespindle shaft 106. Electromagnetic forces are used to rotate the hub 98about the stationary shaft 106 at a desired velocity. Rotationalmovement of the hub 98 is translated to each of the disks 16 of the diskpack 102, causing the disks 16 to rotate with the hub 98 about the shaft106.

The disks 16 are rotated about the shaft 106 at a high rate of speed,and consumer demand for quicker data retrieval can result in increasedrotational speed of the hub 98 and the disks 16 to provide reduced timein accessing data. Even minor imbalances of the rotating motor/diskassembly 102 can generate significant forces that can adversely affectthe ability to accurately position the head 36 relative to the desiredtrack of the corresponding disk 16 while reading from or writing to thedisk 16. Excessive imbalance can degrade the disk drive performance notonly in terms of read/write errors, but also in terms of seek times.Excessive imbalance may result in an undesirable acoustic signature andmay even result in damage or excessive wear to various disk drivecomponents.

The inner diameter 18 of each disk 16 is slightly larger in diameterthan an outer periphery of the spindle motor hub, or rotatable hub 98,in order to allow the disks 16 to slip about the spindle motor hub 98during installation. During assembly, the disks 16 may be positioned inan inexact concentric manner about the spindle motor hub 98. In fact, insome instances, the disks 16 may be intentionally biased against thespindle motor hub 98. This inexact concentric relationship between thedisk 16 and the motor hub 98 results in the disk pack 102 becomingimbalanced. This imbalance can be manifest in at least two respects.

First, the rotating mass of each disk 16 results in a centrifugal forceradially extending in a direction from the axis of rotation 24 in aplane orthogonal to the axis of rotation 24. This can be referred to asa single plane or “static” imbalance. Second, the same centrifugal forcealso results in a moment about an axis, extending from the axis ofrotation 24, as a result of the coupling of two different planes ofimbalance, each of which are orthogonal to the axis of rotation 24. Thiscan referred to as a dual plane, two plane, or “dynamic” imbalance.

Balancing of the disk pack 102 is preferably conducted, for example, bythe manufacturer or during an assembly process, prior to shipping thedrive 10 to the consumer. Single plane balancing of the disk pack 102can include attaching one or more weights to one side of the disk pack102. Not all imbalances may be alleviated to the desired degree bybalancing within a single plane. Dual plane balancing of the disk pack102 can be achieved by attaching one or more weights at two differentelevations along the axis 24 corresponding with vertically spacedreference planes in an attempt to improve upon the potentialinadequacies of a single plane balance.

Balancing the disk pack 102 can be accomplished by attaching one or moreweights to a central portion of the disk pack 102. For example, asillustrated in FIG. 2, the disk pack 102 can have a portion that holdsthe one or more weights or to which the one or more weights attach. FIG.2 illustrates a disk pack 102 having a rotatable hub 98 that includes adisk clamp 100 having a plurality of disk clamp apertures 110 positionedcircumferentially about a central portion of the disk pack 102.

The disk clamp apertures 110 can be, as illustrated in FIG. 2,substantially equidistant from, or equally spaced about, from the axisof rotation 24. For example, a plurality of the disk clamp apertures 110can be positioned about the axis of rotation 24 on a common referencecircle having its center coinciding with the axis of rotation 24. Theplurality of disk clamp apertures 110 can also include apertures thatare positioned at different radial distances from the axis of rotation24 than others of the plurality of disk clamp apertures.

In one embodiment, the disk clamp 100 includes eight disk clampapertures 110 that are positioned about the axis of rotation 24. Thedisk clamp 100 can include between about four disk clamp apertures 110and about eight disk clamp apertures 110. In one embodiment, the diskclamp 100 can include less than four disk clamp apertures 110, and insome embodiments, the disk clamp 100 can include more than eight diskclamp apertures 110.

The disk clamp apertures 110 can be designed to be substantially thesame size, and in some embodiments, the disk clamp apertures 110 can bedesigned to have apertures of different sizes. The different sizedapertures can be positioned with different radial distances as aperturesof different sizes, or the different sized apertures can be positionedwith equal radial distances from the axis of rotation than apertures ofdifferent sizes.

When balancing the disk pack 102, one or more weights can be placedwithin one or more of the disk clamp apertures 110 in order to stabilizethe disk pack 102 during operation. One or more weights can be used tooffset imbalances that are generated during operation of the disk drive10. For example, if imbalances are created by rotational movement of thedisk pack 102 during operation of the disk drive 10, one or more weightscan be placed within disk clamp apertures 110 in order to offset theimbalance created by rotational movement of the disk pack 102.

FIG. 3 illustrates a partially exploded view that includes a disk clamp100 that can be positioned on a disk pack 102 that includes one or moredisks 16. As explained, the disk clamp 100 can include a plurality ofdisk clamp apertures 110 positioned about the axis of rotation 24. Asdepicted in FIG. 3, the disk clamp apertures 110 can be positioned withsubstantially equal radial distances from the axis of rotation 24, suchthat the disk clamp apertures 110 are positioned along a commonreference circle that has its center substantially coinciding with theaxis of rotation 24.

Each of the disk clamp apertures 110 defines a disk clamp aperture axis112 that extends substantially through the respective disk clampaperture 110. The disk clamp aperture axis 112 of each of the respectivedisk clamp apertures 110 can be substantially parallel to the axis ofrotation 24. In some embodiments, the disk clamp aperture axis 112, ofone or more of the disk clamp apertures 110 can be positioned at anglesrelative to the axis of rotation 24. For example, in some embodiments,the disk clamp aperture axis 112 can be positioned at an angle ofbetween about 20° to about 80° relative to the axis of rotation 24, andin some embodiments, the disk clamp aperture axis 112 can be positionedat an angle of between about 30° to about 50° relative to the axis ofrotation 24.

In one embodiment, the disk clamp apertures 110 are positionedsymmetrically about the axis of rotation 24. In some embodiments, thedisk clamp 100 can include disk clamp apertures 110 that are positionedasymmetrically about the axis of rotation 24. And in some embodiments,the disk clamp 100 can include some disk clamp apertures 110 that aresymmetrically about the axis of rotation 24 and other disk clampapertures 110 that are positioned asymmetrically about the axis ofrotation 24.

A fastener 114 can be provided to secure the disk clamp 100 to the diskpack 102. As illustrated in FIG. 3, the fastener 114 can be positionedto be substantially aligned with the axis of rotation 24. The fastener114 is preferably threadingly received by an internal bore in the shaft106.

FIG. 3 depicts a balance plug 120 that can be positioned in one or moreof the disk clamp apertures 110 to balance the disk pack 102. Asillustrated, the balance plug 120 is configured to be sized such that itcan be received within, and preferably through, the disk clamp aperture110. Although FIG. 3 depicts only one balance plug 120 being receivedwithin a disk clamp aperture 110, the disk pack 102 can include aplurality of balance plugs 120 that are received into at least one ofthe disk clamp apertures 110.

FIG. 4A illustrates one embodiment of the motor hub 98 having aplurality of motor hub recesses 124. In one embodiment, the motor hub 98can have a plurality of motor hub recesses 124 positioned in symmetricalfashion about a central portion of the motor hub 98. The motor hubrecesses 124 are preferably constructed to receive therein a balanceplug 120. In one embodiment, the motor hub recess 124 has across-sectional dimension, which can be a diameter, that is less than across-sectional dimension of the balance plug 120. In such embodiments,the balance plug 120 can be received into the motor hub recess 124 bydeforming at least a portion of the balance plug 120. FIG. 4Aillustrates an embodiment of the motor hub 98 that is receiving abalance plug 120 in a first rotation. FIG. 4B illustrates an embodimentof the motor hub 98 receiving a balance plug 120 in a rotation differentthan that of FIG. 4A. FIG. 4C illustrates an embodiment of the motor hub98 receiving another embodiment of a balance plug 120 within a motor hubrecess 124.

FIG. 5 illustrates a partial cross-sectional view of a portion of thedisk pack 102 that includes a rotatable motor hub 98 and a motor orspindle shaft 106 positioned about an axis of rotation 24. The disk pack102 can include a plurality of disks 16 that are secured in position bya disk clamp 100. The disk clamp 100 can include a plurality of diskclamp apertures 110 that are positioned about the disk clamp 100 at aradial distance from the axis of rotation 24.

A motor hub recess 124 can extend from a top surface 126 of the motorhub 98. As illustrated, in one embodiment, the motor hub recess 124extends into the motor hub 98 but does not extend to a bottom surface128 of the motor hub 98. The motor hub 98 can include a plurality ofmotor hub recesses 124 that are positioned about the axis of rotation.

In one embodiment, each of the plurality of motor hub recesses 124 ispositioned about the axis of partition 24 at a radial distance that issubstantially the same as others of the plurality of motor hub recesses124. The motor hub recesses 124 can be positioned symmetrically aboutthe axis of rotation, and in some embodiments, the motor hub 98 caninclude motor hub recesses 124 that are positioned asymmetrically aboutthe axis of rotation 24. The motor hub recesses 124 can be positionedabout the axis of rotation 24 such that each of the motor hub recesses124 is aligned along a common reference circle having its centersubstantially coinciding with the axis of rotation 24. In someembodiments, the motor hub recess 124 can extend into the motor hub 98in a direction that is substantially parallel to the axis of rotation24.

As illustrated in FIG. 5, disk clamp 100 is preferably positionedrotationally about the axis of rotation 24 such that at least one diskclamp aperture 110 is substantially aligned with at least one motor hubrecess 124. In some embodiments, this orientation will permit receipt ofa balance plug 120 into at least a portion of the motor hub recess 124through the disk clamp aperture 110.

In one embodiment, at least one of the motor hub recess 124 and the diskclamp aperture 110 includes a cross-sectional dimension that is lessthan a cross-sectional dimension of the balance plug 120. For example,in one embodiment, the motor hub recess 124 can include across-sectional dimension, which can be a diameter of the recess 124,that is less than a cross-sectional dimension, which can be a diameter,of the balance plug 120. In another example, in one embodiment, the diskclamp aperture 110 can include a cross-sectional dimension, which can bea diameter of the aperture 110, that is less than a cross-sectionaldimension, which can be a diameter, of the balance plug 120.

Accordingly, in some embodiments, when the balance plug 120 is receivedinto the disk clamp aperture 110, and in some embodiments into the motorhub recess 124, the balance plug 120 engages at least one of the diskclamp aperture 110 and the motor hub recess 124. In some embodiments, atleast a portion of the balance plug 120 is compressed or deformed,plastically or elastically, when received into the disk clamp aperture110, or when residing within the motor hub recess 124.

FIG. 6A illustrates one embodiment of a balance plug 120 having aspherical body 140. The balance plug 120 can be used in connection withother embodiments described herein. The spherical body 140 preferablyincludes an outer surface 142 that has at least three retaining portions144 extending therefrom. In one embodiment, each retaining portion 144extends about a portion of the outer surface 142, such that theretaining portion 144 defines an arc along the outer surface 142. In oneembodiment, the retaining portion 144 extends about half way around theouter surface 142 of the spherical body 140. Accordingly, each retainingportion 144 can define a plane in which the retaining portion 144 iscontained. In one embodiment, the retaining portions 144 define at leasttwo intersecting planes. Intersection of the planes can be, for example,along the outer surface 142, as illustrated in FIG. 6A by intersectionregion 146.

In some embodiments, the balance plug 120 can have retaining portions144 that define one or more meridians about the outer surface 142 of thespherical body 140. As used herein, the term “meridian” is used in itsordinary sense and is a broad term, which can include, withoutlimitation, a portion of an arc. The term can also include, withoutlimitation, a portion of an arc extending between poles. In someembodiments, the intersection region 146 can constitute a pole.

FIG. 6B illustrates a balance plug 120 having a plurality of retainingportions 144 extending around the outer surface 142 of the sphericalbody 140. As illustrated in FIG. 6B, the balance plug 120 can includefour retaining portions 144. FIG. 6C illustrates a balance plug 120having a plurality of retaining portions 144 extending around the outersurface 142 of the spherical body 140. As illustrated in FIG. 6C, thebalance plug 120 can include five retaining portions 144. In otherembodiments, the balance plug 120 can include more than five retainingportions 144. For example, the balance plug 120 can include 6, 7, 8, 9,or 10 retaining portions 144. In yet further examples, the balance plug120 can include more than 10 retaining portions 144.

In some embodiments, the disk pack 102 can have balance plugs 120 thatall have the same or substantially the same mass. In some embodiments,the disk pack 102 can have balance plugs 120 of different sizes and/orof different mass. For example, in some embodiments, the balance plugs120 can have the same size and have different masses that can bedetermined based on the desired effect that will be created wheninserted into the disk pack 102. As another example, the balance plugs120 can have different sizes and have the same mass, which can also bedetermined based on how the plug 120 will affect performance of the diskpack 102. In yet another example, the balance plugs 120 can be ofdiffering sizes and differing masses.

In one embodiment, the disk drive 10 can include a spindle hub having abalance plug recess 124 along a top surface 126 of the spindle hub 98.The drive 10 can also include a disk clamp 100, coupled to the spindlehub 98, and the disk clamp 100 can have a balance plug aperture 110 thatis positioned substantially over the plug recess 124 of the spindle hub98. The drive 10 can also include a balance plug 120 having asubstantially spherical outer surface 142. In one embodiment, the plug120 includes a plurality of ribs 144 protruding from the spherical outersurface 142 and defining at least three meridians along the outersurface of the sphere. In some embodiments, the at least three meridiansreside in at least two transverse planes. The plug 120 is preferablysized and configured to be received through the plug aperture 110 andinto the plug recess 124.

In one embodiment, plug 120 is sized such that at least two ribs, orretaining portions 144, are fully received within the plug recess 124.Some embodiments provide that each of the plurality of ribs 144 residesin a plane transverse to the planes of others of the plurality of ribs.In one embodiment, at least one of the plurality of ribs 144 comprises acontinuous meridian protrusion. In some embodiments, each of theplurality of ribs 144 has a radial dimension from a center of thesubstantially spherical outer surface 142 that is greater than a radialdimension of the substantially spherical outer surface 142 of the plug120. Some embodiments of the plug provide that the plug 120 can havefrom three to five ribs 144 positioned about the spherical outer surface142. In some embodiments, the plug 120 can have more than five ribs 144.

Some embodiments provide that the plug 120 consists of a single, uniformmaterial. In some embodiments, this single uniform material is apolymer. In other embodiments, the plug 120 can be made of a pluralityof materials. For example, the plug 120 can, in some embodiments, have ametal that forms the spherical body 140 and have a polymer overmolded,over the metal, to form ribs, protrusions, or retaining members 144. Insome embodiments, the plug 120 can be manufactured such that thematerial of the spherical body 140 and the material of one or more ribs144 have differing moduli of elasticity. In another example, the plug120 can be made of two different polymers, and a polymer with a highermodulus of elasticity can form the spherical body 140, while a polymerhaving a lower modulus of elasticity can form one or more of the ribs144. In yet another example, the plug 120 can have a polymer with alower modulus of elasticity form the spherical body 140, and a polymerwith a higher modulus of elasticity form one or more of the ribs 144.

Some embodiments provide that the balance plug 120 can include a bodydefining a substantially spherical outer surface 142 and a plurality ofribs 144 along the spherical outer surface 142. In one embodiment, theribs 144 define at least three meridians along the outer surface 142 ofthe spherical body.

In one embodiment of the balance plug 120, the ribs 144 extend along theouter surface 142 of the spherical body 140 in a continuous manner. Insome embodiments, the ribs 144 can be segmented or extend only partiallyalong the outer surface 142.

Some embodiments provide a method of balancing a disk pack 102 in a diskdrive 10 that can include the steps of providing a disk drive 10 havinga spindle hub 98 with a top surface 126 and providing a disk clamp 100having a balance plug aperture 110 positioned substantially over the topsurface 126 of the spindle hub 98. The method can further includeproviding a balance plug 120 having a substantially spherical outersurface 142 and advancing the plug through the plug aperture 110 of thedisk clamp 100. The method can further include retaining the balanceplug 120 between the spindle hub 98 and the disk clamp 100 by aplurality of ribs 144 along the spherical outer surface 142 of the plug120, the plurality of ribs 144 can define at least three meridians alongthe spherical outer surface 142. In some embodiments, the method furtherincludes advancing a plurality of balance plugs through the disk clamp.

The description of the invention is provided to enable any personskilled in the art to practice the various embodiments described herein.While the embodiments have been particularly described with reference tothe various figures and disclosure, it should be understood that theseare for illustration purposes only and should not be taken as limitingthe scope of the inventions.

There may be many other ways to implement the embodiments. Variousfunctions and elements described herein may be partitioned differentlyfrom those shown without departing from the spirit and scope of thedisclosure. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and generic principles definedherein may be applied to other embodiments. Thus, many changes andmodifications may be made to embodiments, by one having ordinary skillin the art, without departing from the spirit and scope of thedisclosure.

A reference to an element in the singular is not intended to mean “oneand only one” unless specifically stated, but rather “one or more.” Theterm “some” refers to one or more. Any headings and subheadings are usedfor convenience only, do not limit the disclosure, and are not referredto in connection with the interpretation of the description of thedisclosure. All structural and functional equivalents to the elements ofthe various embodiments described throughout this disclosure that areknown or later come to be known to those of ordinary skill in the artare expressly incorporated herein by reference and intended to beencompassed by the disclosure. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the above description.

What is claimed is:
 1. A balance plug for a disk drive that has a spindle hub having a plug recess, the balance plug comprising: a body defining a substantially spherical outer surface and sized to be received into the plug recess; and a plurality of ribs along the spherical outer surface and defining at least three meridians along the spherical outer surface.
 2. The plug of claim 1, wherein the at least three meridians reside in at least two transverse planes.
 3. The plug of claim 1, wherein each of the plurality of ribs reside in planes transverse to planes of the other of the plurality of ribs.
 4. The plug of claim 1, wherein at least one of the plurality of ribs comprises a continuous meridian protrusion.
 5. The balance plug of claim 1, wherein the balance plug consists of a uniform material.
 6. The balance plug of claim 5, wherein the uniform material comprises a polymer.
 7. The balance plug of claim 1, wherein each of the plurality of ribs has a radial dimension from a center of the substantially spherical outer surface that is greater than a radial dimension of the substantially spherical outer surface of the balance plug.
 8. The balance plug of claim 1, wherein the plurality of ribs consists of from three to five ribs positioned about the spherical outer surface.
 9. The balance plug of claim 1, wherein the balance plug comprises a plurality of materials.
 10. The balance plug of claim 9, wherein the protrusion comprises a material having a different modulus of elasticity than other materials of the balance plug. 